I don't mean to be too callous here but I feel that you should simply stay out of this situation as much as possible. I realize that these folks have become good friends so treat it as simply that. Just because you had sex with them really doesn't make you sages that will solve their problems.
One thing that we have kept in mind throughout our adventures is that our separation of love and sex occurs with our relationships with other couples also. There have been a few couples that we have stopped seeing because they were a little too eager for a good friendship. Simply because I have sex with this guy's wife doesn't automatically make him my best friend. Hell, my best friend doesn't swing but I love him like a brother. It would take years for another couple to truly develop a loving relationship with my wife and me. So, what I'm really saying is it's their problem and their loss (from what I've read from you guys.)
As for questioning your desire to swing. Well, as you know only you can answer that. I will point out that the idea of swinging is a break from the norm. You have already changed your thinking contrary to our societal dogma. When our culture tells you that extra-marital sex with ruin your life you have chosen to ignore it. Why suddenly pay attention to the experiences of one couple who obviously has severe communication problems.
One of my pleasures of hanging out with other men that swing is that they rarely tell me about any marital problems. My straight friends sometimes do and it bugs me. I’m not saying that swinging couples don’t have problems, simply that the successful ones rarely consider talking with anyone else other than their spouse. Usually that solves the problem rather quickly. It’s this team mentality that I enjoy. And, when I see a couple discussing problems with others instead of their spouse, that’s when the flags go up (and we usually go elsewhere.)